<template>
  <div class="carousel-item-container" ref="container" @mousemove="handleMouseMove" @mouseleave="handleMouseLeave">
    <div class="carousel-img" ref="image" :style="imagePosition">
      <ImageLoader @load="this.showWords" :src="carousel.bigImg" :placeholder="carousel.midImg"/>
    </div>
    <div class="title" ref="title">{{ carousel.title }}</div>
    <div class="desc" ref="desc">{{ carousel.description }}</div>
  </div>
</template>

<script>
import ImageLoader from "@/components/ImageLoader"
export default {
  props: {
    carousel: {
      type: Object,
      required: true,
      default: () => {}
    }
  },
  components: {
    ImageLoader
  },
  data() {
    return {
      titleWidth: 0,
      descWidth: 0,
      containerSize: null,
      innerSize: null,
      mouseX: 0,
      mouseY: 0
    }
  },
  computed: {
    imagePosition() {
      if(!this.innerSize || !this.containerSize) return
      const extraWidth = this.innerSize.width - this.containerSize.width
      const extraHeight = this.innerSize.height - this.containerSize.height
      const left = (-extraWidth / this.containerSize.width) * this.mouseX
      const top = (-extraHeight / this.containerSize.height) * this.mouseY
      return {
        transform: `translate(${left}px, ${top}px)`
      }
    },
    center() {
      return {
        x: this.containerSize.width / 2,
        y: this.containerSize.height / 2
      }
    }
  },
  mounted() {
    this.titleWidth = this.$refs.title.clientWidth
    this.descWidth = this.$refs.desc.clientWidth
    this.setSize()
    this.mouseX = this.center.x
    this.mouseY = this.center.y
    window.addEventListener("resize", this.setSize)
  },
  beforeDestory() {
    window.removeEventListener("resize", this.setSize)
  },
  methods: {
    showWords() {
      this.$refs.title.style.visibility = "visible"
      this.$refs.title.style.width = 0
      this.$refs.title.clientWidth
      this.$refs.title.style.transition = "1s"
      this.$refs.title.style.width = this.titleWidth + "px"

      this.$refs.desc.style.visibility = "visible"
      this.$refs.desc.style.width = 0
      this.$refs.desc.clientWidth
      this.$refs.desc.style.transition = "2s 1s"
      this.$refs.desc.style.width = this.descWidth + "px"
    },
    setSize() {
      this.containerSize = {
        width: this.$refs.container.clientWidth,
        height: this.$refs.container.clientHeight
      }
      this.innerSize = {
        width: this.$refs.image.clientWidth,
        height: this.$refs.image.clientHeight
      }
    },
    handleMouseMove(e) {
      const rect = this.$refs.container.getBoundingClientRect()
      this.mouseX = e.clientX - rect.left
      this.mouseY = e.clientY - rect.top
    },
    handleMouseLeave() {
      this.mouseX = this.center.x
      this.mouseY = this.center.y
    }
  }
}
</script>

<style lang="scss" scoped>
@import "~@/styles/var.scss";
.carousel-item-container {
  width: 100%;
  height: 100%;
  color: #fff;
  position: relative;
  overflow: hidden;
  .carousel-img {
    width: 110%;
    height: 110%;
    position: absolute;
    left: 0;
    top: 0;
    transition: 0.3s;
  }
  .title, .desc {
    position: absolute;
    letter-spacing: 3px;
    left: 30px;
    color: #FFF;
    text-shadow: 1px 0 0 rgba(0, 0, 0, 0.5), -1px 0 0 rgba(0, 0, 0, 0.5), 0 1px 0 rgba(0, 0, 0, 0.5), 0 -1px 0 rgba(0, 0, 0, 0.5);
    white-space: nowrap;
    overflow: hidden;
    visibility: hidden;
  }
  .title {
    top: calc(50% - 40px);
    font-size: 2em;
  }
  .desc {
    top: calc(50% + 20px);
    font-size: 1.2em;
    color: lighten($gray, 20%);
  }
}
</style>